A digital signal computer, or digital signal processor (DSP), is a special purpose computer that is designed to optimize performance for digital signal processing applications, such as, for example, fast Fourier transforms, digital filters, image processing, signal processing in wireless systems, and speech recognition. Digital signal processor applications are typically characterized by real time operation, high interrupt rates and intensive numeric computations. In addition, digital signal processor applications tend to be intensive in memory access operations and to require the input and output of large quantities of data. Digital signal processor architectures are typically optimized for performing such computations efficiently.
Embedded processors may include a digital signal processor, a microcontroller and memory on a single chip. A complete system typically includes additional off-chip memory. Minimizing memory access times for high performance digital signal processors and microprocessors is critical in order to maximize processor performance. When the processor requires data or code from off-chip memory, the processor is stalled until the data can be read and returned. Synchronous dynamic random access memory (SDRAM) is widely used in high performance DSP and microprocessor systems, and the latency to read data from this type of memory can be very long.
Accordingly, there is a need for improved methods and apparatus for accessing memory with reduced average access times.